How many objects created?

[Simon Cockayne]

Hi,

Assuming x does not refer to anything before this statement...

String x = "first" + "second";

...how many objects are created?

I have seen two explanations:

1) Answer three: One that x refers to, i.e. "firstsecond". One as a result of "first", which nothing refers to and One as a result of "second" that nothing refers to.
2) Answer one: One that x refers to, i.e. "firstsecond". That is all, since "first" and "second" are string literals and NOT objects.

I'd appreciate a clarification for my upcoming exam.

On your marks...get set...go!

Cheers,

Simon.

[John Campbell]

Simon three objects, "first" "second" and "firstsecond", will be created in the string pool. If you now try and create another string say String str = "second" it would refer to the already existing one from the shared string pool and no new object would be created. I think so anyway!!

[John Campbell]

Simon three objects, "first" "second" and "firstsecond", will be created in the string pool. If you now try and create another string say String str = "second" it would refer to the already existing one from the shared string pool and no new object would be created. I think so anyway!!

[Simon Cockayne]

Hi,

So,why does...

String x = new String("xyz");

...create two string objects according to K&B, page 400 - self test answer to Q 3 say, i.e. one referred to by x and the lost string "xyz"?

I would have thought we were creating one just one String object on the heap, i.e. "xyz" and x is referring to it.

All assistance is warmly welcomed.

Cheers,

Si.

[Mike Gershman]

The string literal "xyz" exists in the string literal pool from the start of the program. The unary operator new always creates a new object. The string literal "xyz" is the single operand of the new operator. The result of the new operation is another object on the heap with the value "xyz".

[Simon Cockayne]

Hi Mike,

Thanks for the feedback, I am grateful.

Excuse me for seeming dim, but I want to be clear on this point

Is the string literal "xyz" an object or not?

Thanks,

Si.

[ShivShankar]

Hi Si,
"str" is an anynomous String object.

Shiv
SCJP1.4

[Simon Cockayne]

Hi again,

So...for...

String x = new String("xyz");

A) "xyz" is a String literal, which IS an object on the heap.
B) new String("xyz") creates a second object on the heap and the reference is assign to the String reference x.

Thank you for clearing that up for me and for the collective patience!

Kind regards,

Simon.